Almost all rice grown in Louisiana is irrigated, but drought can still be a threat to crop productivity. By isolating genes that determine drought tolerance and applying them to rice, LSU AgCenter molecular biologist Niranjan Baisakh is developing rice varieties that can survive as long as two weeks without water.
There are a number of ways that plants cope with drought, Baisakh said, and each corresponds to a different gene. For example, some plants stop growing to conserve energy while others roll up their leaves to minimize water loss. A single resistance gene cannot do much alone — so basically, the more, the better.
Certain varieties of rice and other plants deal with and recover from the effects of dry conditions better than others. Baisakh is working to identify exactly which genes make that possible. Eventually, all of those traits can be applied to rice varieties common in Louisiana as "gene pyramids" — a group of genes that all fight drought but in different ways.
Baisakh is not stopping at rice genes, however.
"There are genes from other plants that may impart drought tolerance," he said.
Baisakh is also examining a grass native to the Louisiana coast and highly tolerant of both drought and salinity.
By taking a holistic approach and studying drought coping mechanisms of several varieties of different plants, Baisakh hopes these drought-tolerant gene pyramids may eventually be applicable to other crops facing drought, such as corn, sugarcane and cotton.
Drought is a growing concern for rice farmers across the globe, Baisakh said. Rice consumes about 35 percent of irrigation water used worldwide on all crops.
Drought is problematic for countries like India, where rice is both a staple crop and food for many residents. Baisakh said farmers in these areas typically rely on rain and do not irrigate. If there is not enough water, rice cannot grow well.
Drought is especially a concern in Louisiana’s northern rice-growing parishes.
"The dense clay soil that is common in northern Louisiana does not allow water retention for long, and irrigation is expensive," Baisakh said. "Rice uses a lot of water, so you're also taking away water from other crops that are grown in greater quantities in that area."
Louisiana growers must also contend with the presence of saltwater. Baisakh said salt causes plant roots to take up less water, meaning the plant will suffer drought-like physiological effects.
This problem is worsened when there is a real drought because the salt becomes concentrated in a smaller amount of water.
That is one reason why it is important to think and look outside the box — the rice gene pool — to find genes that help plants tolerate drought and its effects.
"Maintaining productivity and sustaining yields under such adverse conditions is the ultimate goal," Baisakh said.